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  1. Freelancers

Oleksandr Chernykh

Offer Oleksandr work on your next project.

Ukraine Lvov, Ukraine
5 months 15 days back
Available for hire available for hire
1 Safe completed
10 months 20 days back
1 client
age 53 years
on the service 4 years
Client profile
  • VPN
  • ubuntu
  • System Administrator
  • postfix
  • freebsd
  • mail
  • mariadb
  • gentoo
  • ubiquiti
  • Linux\UNIX
  • MySQL / PostgreSQL
  • Windows/Linux System Administration
Freelancer Oleksandr C. — Ukraine, Lvov. Core skill — Linux & Unix, Windows

Rating

Successful projects
No data
Average rating
No data
Rating
535
Linux & Unix
22 place out of 186
Windows
1 place out of 254

Language proficiency level

Українська Українська: fluent
Русский Русский: fluent
English English: pre-intermediate

Skills and abilities

Programming

Services

Promotion


Administration

Portfolio


  • Administration of the accounting portal dtkt.ua

    Software & Server Configuration
    Administration of the accounting portal dtkt.ua — example of freelancer's portfolio work in category Software & Server Configuration
    • setup and maintenance of the portal 24/7
    • organization of a corporate mailing list server (one mailing list can be up to 250,000 subscribers). Sending speed 10000 emails per minute

    #administration #sysadmin #mail #Windwos #linux #freebsd #mail #postfix #MySQL #mariadb #terminal #nginx

  • Domain controller without Windows

    Software & Server Configuration
    Domain controller without Windows — example of freelancer's portfolio work in category Software & Server Configuration
    • Set up the domain controller on Samba
    • Configured remote user management for the domain
    • Implemented Roaming Profiles for user convenience
    • Set up remote user administration
    …
    This solution saved the company $1200 on purchasing a Windows server

    #administration #sysadmin #Windows #linux

  • and MEDOC. Migration to PostgreSQL Database

    Software & Server Configuration
    and MEDOC. Migration to PostgreSQL Database — example of freelancer's portfolio work in category Software & Server Configuration
    I made the transition from the FireBird BD to PostgreSQL thanks to which MEDOC started to work faster

    #Administration #Sissadmin #Post #Windwos #linux #freebsd #mail #postfix #MySQL #mariadb #terminal #nginx

  • Backup and recovery of MEDOC using PostgreSQL tools

    Databases & SQL
    Backup and recovery of MEDOC using PostgreSQL tools — example of freelancer's portfolio work in category Databases & SQL
    Who has been using MEDCOM for a long time knows that there is not always an opportunity to restore from a backup using standard tools (as it was after updating to version 11.02.144). Therefore, it is also good to make backups using database tools and restore to a new database without affecting the old one

    #administration #sysadmin #mail #Windows #linux #freebsd #mail #postfix #MySQL #mariadb #terminal #nginx

  • Cloning ESXi flash drive online

    System & Network Administration
    Cloning ESXi flash drive online — example of freelancer's portfolio work in category System & Network Administration
    The flash drive device is not completely reliable, especially if it is constantly running. After installing VMware ESXi on the flash drive and configuring vSphere, virtual machines, etc., it is highly, highly recommended to clone it or at least create an image from it for quick replacement in case of failure. And this happens not so rarely

    #administration #sysadmin #mail #Windows #linux #freebsd #mail #postfix #MySQL #mariadb #terminal #nginx

  • Blocking temporary email addresses

    Software & Server Configuration
    Blocking temporary email addresses — example of freelancer's portfolio work in category Software & Server Configuration
    It is known that there are services that provide the opportunity to obtain a temporary email address for free for user web-cabinet registration purposes. Over time, these addresses become invalid, and subsequent mailings to clients of the portal with non-existent addresses negatively affect the domain rating and others. Now, this possibility has been eliminated.

    #administration #sysadmin #mail #Windows #linux #freebsd #mail #postfix #MySQL #mariadb #terminal #nginx

  • Solved the bounce loop or reply looping problem

    Software & Server Configuration
    Solved the bounce loop or reply looping problem — example of freelancer's portfolio work in category Software & Server Configuration
    The organization sends informational messages (advertisements, promotions, news, etc.) to its subscribers. All subscribers validated their emails during the user account registration process. All messages are received through a separate mail server. The standard number of messages in the queue that have not been sent immediately is up to 1000, which is considered normal. Usually, 3-5 mailing sessions are conducted per day. Suddenly, the number of messages in the queue started to increase. Such behavior is considered abnormal.

    #administration #sysadmin #mail #Windows #linux #freebsd #mail #postfix #MySQL #mariadb #terminal #nginx

  • Mailing server

    Software & Server Configuration
    Mailing server — example of freelancer's portfolio work in category Software & Server Configuration
    Configured the corporate portal email newsletter server. One newsletter can reach up to 250,000 subscribers. Sending speed is 10,000 emails per minute. Number of newsletters is 3-5 within a working day. The mailing log is recorded in the database for further analysis by call center managers.

  • Mail routing

    Software & Server Configuration
    Mail routing — example of freelancer's portfolio work in category Software & Server Configuration
    To prevent blocking of the server address from which mailings are sent in various blacklists, I configured mail routing through different interfaces (IP addresses) of the mail server

    #administration #sysadmin #mail #Windows #linux #freebsd #mail #postfix #MySQL #mariadb #terminal #nginx

  • SHADOW mode for unprivileged user on WIN-server

    Software & Server Configuration
    SHADOW mode for unprivileged user on WIN-server — example of freelancer's portfolio work in category Software & Server Configuration
    Gave the ability for a non-privileged user to connect to other users' terminal sessions (shadow mode)

    #administration #sysadmin #mail #Windows #linux #freebsd #mail #postfix #MySQL #mariadb #terminal #nginx

  • Simultaneous operation of OpenVPN server over TCP and UDP protocols

    System & Network Administration
    Simultaneous operation of OpenVPN server over TCP and UDP protocols — example of freelancer's portfolio work in category System & Network Administration
    For user convenience, ensured simultaneous operation of the OpenVPN server over TCP and UDP protocols

    #administration #sysadmin #mail #Windows #linux #freebsd #mail #postfix #MySQL #mariadb #terminal #nginx

  • Simultaneous use of two VPN connections

    System & Network Administration
    Simultaneous use of two VPN connections — example of freelancer's portfolio work in category System & Network Administration
    Ensured the user can work simultaneously with different clients through separate VPN connections

    #administration #sysadmin #mail #Windows #linux #freebsd #mail #postfix #MySQL #mariadb #terminal #nginx

  • Postal server by kadroland.com

    Software & Server Configuration
    Postal server by kadroland.com — example of freelancer's portfolio work in category Software & Server Configuration
    Configuration of the mail server for mailing

    #Administration #Sissadmin #Post #Windwos #linux #freebsd #mail #postfix #MySQL #mariadb #terminal #nginx

  • Solving the issue of slow mail sending

    Software & Server Configuration
    Solving the issue of slow mail sending — example of freelancer's portfolio work in category Software & Server Configuration
    Problem on the corporate mailing list server

    E-mail messages on ukr.net slowly began to leave. As it turned out from the correspondence with their support, they have changed a number of rules for receiving mail

    … Work results
    - A flexible, scalable system for delivering letters to different mail providers with smtp restrictions on the input has been received
    - Consumed resources CPU / RAM increased slightly
    - Slightly more difficult to administer the system

    #administration #sysadmin #mail #Windwos #linux #freebsd #mail #postfix #MySQL #mariadb #terminal #nginx

  • Work in accounting outsourcing

    System & Network Administration
    Work in accounting outsourcing — example of freelancer's portfolio work in category System & Network Administration
    • local network administration
    • corporate mail
    • setting up and maintaining a terminal server
    • setting up remote access to the terminal
    … • communication with the company's clients
    • other jobs

    The complex of works carried out allowed not only employees to connect remotely, but also to attract the company's clients to work with the server remotely

    #administration #sysadmin #mail #Windwos #linux #freebsd #mail #postfix #MySQL #mariadb #terminal #nginx
Show more 7 jobs

Reviews and compliments on completed projects 1

13 July 2025 16 USD
One-time work on Windows

Quality
Professionalism
Cost
Contactability
Deadlines

We talked with Oleksandr, everything is good, I liked it

Natalya Grevtsova | Personal | Response review

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